Adverbial: Time (Cuando, Hasta que) | Spanish (Latin America) Grammar

Time conjunctions like cuando (when), hasta que (until), and en cuanto (as soon as) are especially interesting because they can take either the subjunctive or the indicative. The mood depends entirely on whether the action in the subordinate clause is future or habitual/past.

The rule

Future event (hasn't happened yet) → subjunctive
Habitual event (always happens) or past event (already happened) → indicative

Time conjunction + subjunctive = future, uncertain Time conjunction + indicative = routine or past fact

Cuando venga, hablaremos.

When he comes, we'll talk. (future — hasn't happened)

Cuando viene, hablamos.

When he comes, we talk. (habitual — every time he comes)

These two sentences look almost identical in English, but Spanish insists on distinguishing them. The first describes a specific, anticipated future visit. The second describes a repeated pattern.

The time conjunctions

All of these can take either mood depending on time reference:

cuando — when
hasta que — until
en cuanto — as soon as
tan pronto como — as soon as
después de que — after
antes de que — before (always subjunctive — see below)
mientras — while, as long as
una vez que — once, as soon as
siempre que — whenever

With the exception of antes de que, which always takes the subjunctive, all of these conjunctions flip moods based on whether the action is future-looking or not.

Future actions: subjunctive

When the main clause describes something that will happen, and the time clause describes a condition that also lies in the future, the subjunctive is required. The time clause refers to a moment that has not yet arrived.

Te llamaré en cuanto llegue a casa.

I'll call you as soon as I get home.

No saldremos hasta que termine la lluvia.

We won't leave until the rain stops.

Tan pronto como lleguen los invitados, serviremos la cena.

As soon as the guests arrive, we'll serve dinner.

Notice that the main clause is usually in the future tense, the present (with future meaning), or a command. This is a strong clue that the subordinate clause is also future and therefore subjunctive.

Habitual actions: indicative

When the time clause describes something that always or usually happens, use the indicative. The action is presented as a routine or general truth, not as a pending event.

Cuando llueve, me quedo en casa.

When it rains, I stay home. (every time)

Mi hija lee hasta que se duerme.

My daughter reads until she falls asleep. (routine)

En cuanto suena el despertador, me levanto.

As soon as the alarm rings, I get up. (every morning)

Past actions: indicative

If the time clause refers to something that already happened in the past, it takes the indicative. The action is a completed fact.

Cuando llegué a la fiesta, ya no había nadie.

When I arrived at the party, there was no one left.

Estudié hasta que me cansé.

I studied until I got tired.

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The fastest test: if the main verb is in the future tense, conditional, or a command, the time clause is almost certainly subjunctive. If the main verb is in the present habitual or the past, the time clause is almost certainly indicative.

Antes de que: always subjunctive

Antes de que (before) is the exception. It always takes the subjunctive, regardless of time reference. The logic: anything that happens before something else is by definition not yet when the "something else" occurs, so it is always framed as anticipatory.

Quiero terminar antes de que llegue mi jefe.

I want to finish before my boss arrives.

Siempre como algo antes de que empiece la clase.

I always eat something before class starts.

Even in the second example, where the action is habitual, antes de que still takes the subjunctive. This is unique among the time conjunctions.

Mientras: two meanings

Mientras can mean "while" (simultaneous action) or "as long as" (conditional). With the indicative, it means "while" in a descriptive sense. With the subjunctive, it often leans toward a conditional "as long as."

Mientras cocino, escucho música.

While I cook, I listen to music. (habitual, descriptive)

Mientras tengas ganas, puedes seguir.

As long as you feel like it, you can continue. (conditional)

Después de que: regional variation

In theory, después de que follows the same rule as cuando: subjunctive for the future, indicative for the past. In practice, especially in Latin American Spanish, many speakers use the subjunctive even for past events, by analogy with antes de que. Both versions are widely accepted.

Te veré después de que salgas del trabajo.

I'll see you after you leave work. (future — subjunctive)

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If you're uncertain whether a time clause is future or habitual, check the tense of the main verb. A future-tense main verb almost always drags the time clause into the subjunctive.

For a direct comparison of these two moods across several kinds of triggers, see Subjunctive vs Indicative: Key Contrasts.